Electric discharge device



May 21, 1935. v w. F. WESTENDORP 2,

ELECTRIC DISCHARGE DEVICE Filed July 21, 1934 Inventor; Wi Hem FTWestehdmp Patented May 21, 1935 UNITED-STATES PATENT oFFic'E ELECTRICDISCHARGE DEVICE Willem r. Westendorp, Schenectady, N. 1.," ,usignor toGeneral Electric Company, a corporation of New York Application July21., 1934, Serial No. 738,383

4 Claims.

"a preheating of the cathode is required.

For abetter understanding of my invention, together with other andfurther objects thereof, reference is had to the following description,taken in connection with the accompanying drawing, and its scope will bepointed out in the appended claims.

In the accompanying drawing, Fig. l illustrates diagrammatically anelectric discharge lamp of the hot cathode type connected in accordancewith my invention to a single transformer which supplies both thedischarge current and the cathode heating current; Fig. 2 illustratesdiagrammatically a hot cathode discharge lamp connected to a directcurrent series circuit and arranged; in accordance with my invention,for automatic preheating of the cathode before each starting of thelamp.

Referring to Fig. 1 in detail, the primary winding i of the transformer2 is connected into a constant current circuit. The transformer 2 isprovided with a single core 8 and secondary windings 4, 5 and i. Thesecondary windings are connected to an electric discharge lamp I whichis provided with a pair of anodes 8 and 9, a pair of cathodes i and Iicomprising metal filaments and a glass envelope l2. The anode 8 isconnected to cathode l0 and the anode 8 is connected to cathode ll sothat when, during operation, alternating current is provided, each ofthe structures operates alternately as an anode and as a cathode. Thewinding 4 is connected to the ends of cathode II by the conductors I!and i4 and the winding 8 is connected to cathode H by the conductors i5and It The conductors i4 and I5 are also connectedrespectively to thewinding 5 and to the ends of the cathodes l8 and II which are remotefrom the anodes 8 and 8, so that the current circulating through winding5 must necessarily flow through the two cathodes and the discharge pathbetween the anodes 8 and 8 in series.

The primary winding I of the transformer 2 being connected in a constantcurrent circuit produces a substantially constant average flux forexciting the windings 8, 5 and 8. It is, therefore, necessary tomaintain the lead on these three windings substantially constant toprevent an undue unbalancing of the available energy which would occurif one section were open 10 circuited. Such condition would overload theclosed circuited section of the winding and raise beyond safe limits thevoltage across the terminals oi the open-circuited section.

In the arrangement in accordance with my invention, I provide a timedelay thermostatic switch ii for opening and closing a shunt circuitabout the discharge path in the lamp, this circuit being arranged tocarry full load current when closed. The switch I! is provided with a 2pair of contacts I! and IS, a thermostatic member 28 for moving thecontact I8 into and out of engagement with contact l9 and a heater 2|for causing the member to operate. The contact i8 is connected in serieswith a loading rewhen current begins to flow through the winding I, thecontacts i8 and I! are in engagement and a current equal to normal loadcurrent flows through the resistor .22. The-windings l and 6 are alsoexcited and being permanently connectedto the cathodes l8 and il heatthem. The

heater 2! in the meantime is also energized by the winding 6. Theheating of this element is so arranged that a predetermined time periodelapses before it deflects and thereby opens the 40 circuit. Thecathodes are thereby given time to rise to the proper temperature beforestarting .potential is applied across the lamp. When the thermostaticswitch operates, the contacts l8, I!

open and the potential of winding 5 is applied to the lamp. If thedischarge does not start instantaneously the temperature of thefilaments is automatically increased and the potential of the winding 5also is increased so that the present arrangement provides theadditional voltage necessary for starting the lamp.

The above circuit provides in effect a shunt operation of the cathodesand the discharge path, because there is a division of the availableenergy between the transformer winding sections. I

have provided an equivalent circuit for operating a lamp with directcurrent as is shown in Fig. 2. Fig. 2 illustrates an electric dischargelamp 25 provided with an anode 26, a cathode 21 and a cathode heater 28.The heater 28 is preferably a metal filament connected at one end to thecathode and at the other end to the anode terminal by a conductor 29;The heater is, therefore, connected in parallel to tlie discharge pathbetween the anode 2E and cathode 21. A second conductive path,connected. in shunt to the discharge path, includes a switch 30 and aresistor 3|. The switch 30 comprises a thermostatic ele ment 32 providedwith a contact 33 which it moves into and out of engagement with contact34 in response to the operation of a heater 35. When the contacts are inengagement, a circuit is closed which may be traced from the cathodeterminal through resistor 3i, conductor 86, contacts 34, 33, element 32,conductor 31 to the anode terminal.

The anode and cathode' terminals are respectively connected into aseries circuit indicated by conductors 38 and 39 to which substantiallyconstant current is supplied. The heater 35 is supplied with currentfrom the line 38 since it is connected in series therewit throughconductors ll, 42 and 37.

In operation when current is first supplied to the series circuitrepresented by the conductors 38 and 39, the total current of thecircuit divides itself between the heater 28 and the shunt circuitthrough resistor 3|. This resistor is adjusted to carry a current equalto the full discharge current. At this arrangement of the circuit,therefore, full operating voltage is applied to the cathode heater 28and across the discharge path between the electrodes of the lamp. Adischarge lamp, however, will not start at normal voltage so that thecathode heater 23 is given time to heat up. In the meantime heater 35raises the temperature of the thermostatic element and causes the latterto separate the contacts 33 and 34 and thereby break the circuit throughresistor 3|. The time interval for the breaking of this circuit is soarranged that the heater 28 is brought to the proper temperature. Whenthe circuit is broken the voltage across the lamp is momentarily raisedand the lamp is started. The total line current then divides between thedischarge path and the cathode heater. If the lamp does not start withina short predetermined time for some reason a film contact 43 connectedbetween conductors it and I breaks down and short circuits the windingsection 5.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. In combination, an electric discharge device provided with an anode,a cathode, a heater for said cathode, a constant current circuit, meansfor dividing the available energy received from said circuit betweensaid cathode heater and the discharge path between said anode andcathode, and a circuit connected in shunt to said electrodes arranged tocarry the normal discharge current until the said cathode has beenpreheated.

2. In combination with an electric discharge lamp provided with athermionic cathode and an anode, a transformer having a primary windingprovided with substantially constant current, a secondary winding havingsections connected across said cathode and said electrodes respectively,a load circuit in shunt to the discharge path between said electrodesfor shunting the normal load current past said discharge path, and atime delay switch for opening said shunt circuit about said dischargepath a predetermined time interval subsequent to the energization of theprimary winding.

3. Incombination, an electric discharge lamp provided with an anode, acathode, a. heater for said cathode and a discharge path between saidanode and cathode, a constant current circuit connected to supplycurrent to said discharge path and heater in multiple, and a shuntcircuit arranged to carry the current of said discharge path until thecathode has been preheated.

4. In combination, an electric discharge device provided with an anodeand a thermionic cathode provided with a heating circuit, a constantcurrent circuit, means for dividing the available energy received fromsaid circuit between said cathode heating circuit and the discharge pathbetween said anode and cathode, and a circuit connected in shunt to saidelectrodes arranged to carry the normal discharge current until the saidcathode has been preheated.

WILLEM F. WESTENDORP.

